Apparatus for generating alternating current



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Patented June 5%, i926.

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FRITZ LOWENSTEIN, OF NEW' YORK, N. Y; JOHN C. WVAIT, ADltIINIfSTRATOIEt01* SAID FRITZ LOWENSTEIN, DECEASED, ASEiIG'NOB, IVIESNE ASSIGNMENTS, TORADIO PATENTS COBFOEA'IION, A DQIQESTIC GOREOlt-ATION.

APPARATUS FOR GENERATING ALTERNATING (DUKE-ENE.

Application f led November 29, 19 18.

lhis invention relates tov apparatus for generating alternating current,and more particularly to oscillation generating sys tems in which asource of direct current is utilized as the source of energy from whichthe alternating current is produced.

I am aware that Various types of systems have been proposed heretofore-for deriving alternating current from direct current, but such systemshave not proved satisfactory in all respects. Some are complex,comparatively ineilicient, and incapable of sufliciently accuratecontrol, while others are incapable of a large power output.

It is, therefore, a principal object of my invention to provideapparatus for generating electrical oscillations, by means of which ahigh efficiency and accurate control may be attained in a simple mannerwith a comparatively large power out-put. Other objects of the inventionwill appear as the description of the invention proceeds.

In one practical form of system embodying my invention, direct currentis supplied to a divided circuit consisting of a plurality of parallelbranches, two in a typical. instance, each of which includes aconductive gap and alternating potential-impressing means cooperatingtherewith. Thus, for example, each parallel branch may include anevacuated vessel of the audion type containing a heated filamentcathode, a plate or wing anode, and a grid interposed in the conductivegap between the cathode and anode. The grids of the audions in theparallel branch circuits are electrically connected to gether, this gridcircuit being electrically interlinked with a frequency-controlling orsteering circuit, which is also electrically interlinked with both ofthe wing circuits. The steering circuit may be a circuit speciallyprovided for the purpose; or the output circuit may be arranged toexercise also the functions of a steering circuit, as will hereinaftermore fully appear. In any case, it is essential to the present inventionthat the i-JtGQllllg circuit, whether it he an output circuit or aspecial auxiliary circuit, shall be capableot sharp tuningf In otherwords, the oscillation decrement oi? the steering circuit should alwaysbe less, and most desirably very much less, than is possible with acircuit containing an iron core, such as repeater circuit of the wellknown type, where Serial No. 264,645.

the oscillation decrement is commonly not less than 0.1. In the practiceof the present nvent on, the oscillation decrement of the steeringcircuit is never as high as that of an lron core or repeater circuit;and in the best embodiments of the invention said decrement is of a muchlower order of mag mtude, say 0.01 or 0.001,in typical examples. Bymeans of such a sharply tunable steering circuit, great accuracy incontrolling the frequency of. the alternating current generated, isattained, as well as other advantages, especially in high trequencvwork. l i hen a system of the character deseribed is in operation morecurrent from the direct current source flows alternately through onewing circuit and then through the other, owing to the modulating effector the interposed grids; and the relation of the wing circuits. to theoutput circuit is such that an alternating current is thereby induced inthe latter. The frequency. of this alternating current is determined andgoverned with extreme accuracy by the sharply tuned steering circuitbefore mentioned which impresses upon thegrid circuit whatever frequencymay be desired, thereby causing an alternating rise and fall ofpotential in the resp ctive grids in such manner that when the potentialof one grid is raised, the other is lowered, and vice versa. Thus themodulating effect of the grids, which is electrostatic in the presentinvention, is positively governed and the output frequency accuratelycontrolled in a regula-ble manner. The frequency may of course beadjusted or varied by suitable adjustment of the constants of thesteering circuit, vs 'hether the latter be the output circuit proper ora special auxiliary circuit.

The objects and novel features of my invention will be. more fullyunderstood,from the. following description taken in connection with thedrawing in which Figs. 1 and 2 are diagrams of systems embodying myinvention.

In the specific embodiments of my invention illustrated in the figuresor the drawing. the, divided circuit consists ftW li branches or wingcircuits}; and Y, to which a battery or other suitable source of directcurrent, is connectedby the conductors and 11. 'llhebattery B togetherwith the conductors lfi aud 11 and thawing circuits X and Y thus form aclosed direct current input circuit for the generating system.

Vacuum tubes T and T, which, for example, may be audion tubes of wellknown cinistruction, are connected in the branch circuits X and Y,respectively, the filaments 12 and 13 thereof being connected byconductors l4 and 15, resp ctively, to the con ductor l0, and beingheated by current from the batteries A and A, respectively, or bycurrent from some other suitable source.

1 The wings or anode plates 16 and 17, cooperatmg with the lilaments l2and 13, re-

spectively, to term parallel conductive gaps, are connected byconductors 18 and 19 to the conductor 11.

The PliClS 20 and 21, constituting alternating potential in'ipressingmeans, are inter posed in the conductive gap between the lilaments andplates of the tubes T and T, respectively. T hese gri ds extend. acrossthe streams of electrons passing from the respective filaments 12 and lbto the plates 16 and 17, and when the respective potentials oi the gridsare varied, as by alternate increase and decrease, the currents 'tlowingin circuits X. and Y are modulated, by the electrostatic effect of thegrids, so as to alternately increase and decrease thetlow of crrent inthe respective wing circuits. The grids 20 and 21. are electricallyconnected together by a conductor 2 that includes a winding 23, by meansof which the potentials on the grids may be accurately controlled orvaried, in a manner to be set forth later.

Most desirably an intcrn'iediate point, usually the mid-point oi": thewinding'fZS, is connected as by lead 23 to a point which may be eitherat substantially the same po tential as the cathodes l2 and .13. or morenegative than said cathodes, (lQPEllCllllQ'1113011 the use to which thesystem is to be put. To rovide for operating under either condi tion,the lead 23 is arranged For adjustable connection at 23" either toconductor 10, for example, or to some point on the battery 1% as in theparticular arrangement illustrated. In the latter case, which is acondition best adapted for telephone work, a potential more negativethan that 01" the cathodes 1:2 and .13. is impressed upon the grids 20and El, and the degree of this ultran itire potential may evidently beadjust-en as desired by shifting the lead connection.

For high frequency work, the connection may be shifted to equalize thegrid and filament potentials.

The output or load c rcuit may comprise any suitable form of energyabsorbing or translating means. its specific example, the load circuitillustrated is a tuned antenna circuit for a wireless telegraph ortelephone transmitter. The antenna circuit embodies an aerial 2i, aground 25, and inductances 26 and 27, which are inductively related,'res)eclively, to inductances 28 and S25) constituting portions of theconductors 1S and 1.) of the wing circuits X and Y, respectively, the an tenna circuit being thereby loosely coupled to both said wingcircuits. Although this arrangementis .i'nost desirable, the antenna maynevertheless be coupled to only one of said wing circuits. It will beunderstood that in the arrangement illi'istrated the coils 26 and 2? areusually and most desirably so wound and connected in the circuit thatthey are mutually assisting.

Particularly in the type of system illustrated, wherein the wingcircuits are also free of iron cores and possess a low oscillationdecrement, only a single wing circuit may be used.

Suitable means are provided to govern the "frequency of the gridpotential alternations. In the arrangement illustrated in Fig. 1, thetuned antenna circuit is utilized as the frequency governing or steeringcircuit. This is accomplished by including in the antenna circuit a.winding 30, which is inductively related to the winding 43 connected tothe grids :20 and 21, and thereby loosely couples the antenna and gridcircuits. As here shown, the antenna circuit also contains a variabletuning inductance 31 by means of which the constants of the antennacircuit may be altered desired to provide for transmitting at differentwave lengths, for example. It is especially to be noted that the antennacircuit in this instance contains no iron core or repeater, and that ithas a small oscillation decrement ot the character previously described.The arrangement illnstrated. wherein the inductances 30 and 3 arebetween coupling induetances 26, 27, and ground, with inductance 3Onearest ground, otters special advantages, and is preferred.

The operation of the system shown in Fig. l is briefly as follows:Direct current being; supplied to the two wing circuits X and Y b thesource of direct current B, pulsating cuiients are up in the wingcircuits by virtue of the circuit cl'iaracteristics; and alternating;current oscillations are induced in the antenna circuit. These latterin'nnediately exercise a predominating influence, through the loosecoupling 30, 23, on the grid potential alternations, each gridhaving;-impressed upon it potentials alternating in synchronism with theantenna. oscillations but substantially out of phase with each other.The frequency ot the antenna oscillations can be adjusted at will byshifting switch device for example, to vary the etiective value ofinductance 31.

It will be observed that simply by shifting a single controlling:member, switch arm in this instance, the frequency of the oscillationsin the antenna or output circuit may be changed to any desired valuewithout adjustmg any other part of the system, The imr 1: oer/secsportance of thisarranggeiuent in enabling, tor example. rapid and easyshittto any desired wave length in transn-nitting radio signals is atonce apparent.

in the arrangement shown in Fig. 2, an auxiliaryltrerpiency-e-ontrollinpj or stecrin); circuit is en, oyed to impress agoverning; alternating )otential. ot the desired uuency on the connectedgrids. This auxiliary circuit may take various forms, but in any casemust be capable of sharp tuning. As here shown it comprises a variablecapacity 33, and inductance of which a part, 34, cooperates with winding23 to loosely couple the grid and steering circuits; while pick-up coils34S and 34;", coo fierating with windings and 29, respectively, looselycouple the steering and the output or antenna circuits. The antennacircuit may include a variable tuninp; capacity 35.

This embodiment of the invention operates in substantially the samemanner as the system of Fig. 1, but the auxiliary tuned circuit governsthe output "frequency, taking; energy from the wing circuits andimpressing upon the grids an alternating potential of predeterminedfrequency.

Aflthough a tuned antenna is shown in Fig. 2, the use of a specialauxiliary steering; circuit is not to be understood as limited to asystem where the output circuit is tuned. On the contrary, an auxiliary,steering circuit is especially useful where it is not desired to havethe output or consumption circuit tuned, or where the consumptioncircuit can not be as sharply tuned as the auxiliary steering circuit.

ll hile the above described systems, which may be called splitters,involve the use of more than one audion or equivalent device, certainfeatures of the invention are evidently applicable to splitter systemsin which only one of the parallel circuits contains such device, theother circuit being in the nature of a by-pass and containing inductanceand capacity, tor example. It is also to be understood that the systemsherein disclosed may, within the invention, be inductively or otherwiseassociated with telephone or other input circuits, provided thesteering; or treq iency-controllinc; circuit be capable of sharp tuning,as hereinbeiore set forth.

What I claim is:

1. A. system for generating alternating current comprising thecombination with a source of direct current, of a pair of thermionicdevices each including an anode, a cathode, and a modulating devicecooperating therewith, parallel circuit connections whereby saidthermionic devices are connected in circuit with said source and inparallel with each other, each of said parallel circuit connectionsincluding an inductive winding, a connection between saidmodulatingdevices, and a sharply tunable circuit inductively coupled tosuch modulating de vice connection in such manner as to producealternating potentials of substantially di'li'ering phase on saidmodulator devices, said sharply tunable circuit including separateinductive windings cooperatingrespectively with the inductive windingsin said parallel circuit connections.

In a system for generating alternating such modulating device connectionin such manner as to produce alternating potentials of substantiallydifliering phase on said modulating); devices, said sharply tunablecircuit includinq separate inductive windings cooperating with therespective inductive windings in said parallel branches.

3. In a system for generating alternating current, the combination witha circuit having a plurality of parallel branches, and means forenergizing; said circuit, of thermionic means having anode, cathode andmodulating means included in each of the parallel branches of saidcircuit, whereby parallel thermionic current paths are provided, aplurality of inductive windings, arranged one in each parallel branch ofthe circuit, a connection bet-ween the different portions of saidmodulating means in said parallel branches, and a separate sharplytunable circuit coupled inductively, only, to such modulating meansconnection in such manner as to produce alternating potentials ofsubstantially differing phase on said difterent portions of saidmodulating means, said sharply tunable circuit including separateinductive windings cooperatiin; with the respective inductive windingsin said parallel branches.

4:. In a system for generating alternating current, the combination witha circuit having a plurality of parallel branches, and mean's forenergizing said circuits, of plurality of thermionic devices, eachincluding; an anode, a cathode and a modulating device, each thermionicdevice having its anoce and cathode included in its respective parallelbranch of the circuit, whereby the thermionic devices are arranged inparallel with each other, a plurality of inductive windings, arrangedone in each parallel branch duce alternating differing phase on saidmodulating dev1ces,.

of the circuit, a connection between said modulating device, a separatecircuit coupled inductively, only, to such modulating device connectionin such manner as to propotentials of substantially said separatecircuit including separate inductive windings cooperating with therespective inductive windings in said parallel branches, and an outputcircuit related to 10 said parallel branches.

In testimony whereof I hereunto afiix my signature.

FRITZ LONENSTEIN.

